YJ - 15 to 20 Gallon Tank Modification - JeepForum.com
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post #1 of 21 Old 11-30-2003, 05:25 PM Thread Starter
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YJ - 15 to 20 Gallon Tank Modification

The weather was nice today so I decided to perform the 20 gallon modification procedure on my Jeep. Since it's a 95, it fit into the 91 thru 95 category where Chrysler made a longer ventilation insert tube instead of actually changing out the tank when customers requested a 20 gallon gas tank. This saved them time because instead of changing the stock 15 gallon tank, they would simple modify the ventilation insert tube length. The whole process only took 2 hours and I could have done it faster if necessary but I was listening to the Steelers lose yet another game on the radio. The first step was to remove the license plate assembly and the filler plate to allow access to those tricky clamps.

The first picture shows one of the top clamps that needed to be removed. The other clamp is hidden and the whole assembly should be removed:

The second picture shows the plastic shroud that needs to be removed to gain access to the lower hose clamp:

The third and fourth pictures show a small 5/16" wrench used to loosen the ventilation hose clamp and the hose itself. Once it's loosened enough you can rotate the hose down so you can remove the clamp from underneath:

The fifth picture shows the actual insert hose being removed. I used a pair of small needle nosed pliers to get the hose started and switched to larger vise grips to finish the removal. This hose is pretty hard to extract so wear some gloves in case your hands slip. In this picture the insert hose in only out about 1/2":

The last two pictures show before and after shots of the insert hose. It started off at 9.5" and I cut it down to 2". I guess you could have done away with it altogether but I wanted it there to help strengthen the outlet when the hose clamp was installed:

Once I put everything back together I filled it up at the local gas station and it took 19.1 gallons. My fuel gauge read 1/8 before I started this project since it's a good idea not to have a full tank when doing this. I am getting 14 mpg, so this free modification allows me 70 more driving miles per tank. I guess the only down side to this is your fuel gauge will read full while the extra 5 gallons are being burned. I have no plans on changing out my 15 gallon sending unit, which is located inside the fuel tank. This was a simple project and I recommend anyone with a 91 - 95 YJ who wants a large gas tank to tackle this job.


EDIT: Imagestation blows some times so here are the pictures cited above - Sorry...








Last edited by Moxley; 04-24-2004 at 10:31 AM.
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post #2 of 21 Old 11-30-2003, 05:34 PM
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I tried this, but couldn't get to the band clamps on the hose. Any secrets or just shoved your hand in. THe angle was off and I couldn't get anything on the clamp screws.


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post #3 of 21 Old 11-30-2003, 05:52 PM Thread Starter
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Hi Craig,

I did get a few scratches on my right hand reaching in with the wrench. I reached in through the back (filler opening) with a small 5/16" open end wrench. The angle was terrible but I was able to rotate the wrench from end to end with small turns until I was able to turn the hose by hand to gain access from the bottom. From there it was easy to remove the clamp.

Good luck,
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post #4 of 21 Old 11-30-2003, 10:22 PM
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ok I'm trying to figure this out.

The reason our tank is only 15 gallon is beacuse a tube hangs in the tank and when the fuel reaches the end of it you can't pump anymore fuel in?

And by doing the modification it makes the hanging tube shorter letting you put more fuel in your tank.?

I'm confused ? please explain if you don't mind (:

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post #5 of 21 Old 12-01-2003, 06:11 AM Thread Starter
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Can't explain it better than you just did because you hit it right on the head. Because the filler ventilation insert tube is sticking down in the gas at the 15 gallon level, it starts spitting fuel back to the nozzle to shut it off. Without that sneaky tube it uses all 20 gallons.

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post #6 of 21 Old 12-01-2003, 08:05 PM
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thanks for the write up moxley. i just happened to have my tank out of my jeep, repairing a split fuel line. It is really easy with the tank out.


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post #7 of 21 Old 12-03-2003, 07:51 AM
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I wish I knew if my Jeep had this done already I bought it 2 weeks ago and the first time I filled it up I put like 14 gallons in and the gauge read between 1/2 and 1/4 tank. The way the gauge bounces around I figured the gauge was busted. I guess the only way of knowing is to run out of gas and see how many gallons it takes to fill it back up.
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post #8 of 21 Old 12-03-2003, 12:21 PM
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i did this mod and i just drilled a hole big enough to get a screwdriver through on the rear floor pan and loosened the clamp. I didnt put ANY of that little vent tube back in either. not a problem and its been over a year and a half since i did it.

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post #9 of 21 Old 12-03-2003, 03:41 PM Thread Starter
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Hi wr70beh,

What I would do if I were you is go ahead and do this procedure since your gauge is obviously giving false readings. This way you could fill it up all the way and know you have about 280 miles per tank (20 gallons x 14mpg average Jeep). It would drive me crazy always having to fill the tank, guessing how much fuel I have.

Good Luck,
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post #10 of 21 Old 12-04-2003, 07:04 AM
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The hose clamp on mine was facing up enough I could not get a tool on it. I took a screw driver and places it under the end of the band and bent it up until I broke the screw adjuster off then just replaced the hose clamp.

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post #11 of 21 Old 06-07-2004, 02:49 AM
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I just finished the mod on mine. The clamps were easily accessed, since all screw adjusters on the clamps were pointed down HOWEVER I had a hell of a time getting the ventilation tubing out of the tank opening. The first two inches of the tubing are completely chewed up from my attempts to pull it out. I was so tired at the end, I didn't bother putting in ANY length of that tubing back into the ventilation tank opening. I read above there wasn't a problem with that so I left the tubing out altogether as well.
And at the gas station racked myself a nice bill up for 69 litres of gas, remembering I wasn't fully empty when I filled up. So the tubing removal DID increase the tank size to about 76litres/20gallons.

I want to thank everyone with their helpful hints, pictures and detailed explainations that made this job much easier...

Oh yeah the timing on this for me was approx. 3 hours...I'm figuring it would have been quicker if that tubing wouldn't have been such a P.I.T.A. to come out of the tank. If the tubing gives quickly and is easily removed I would give this project a good one and a half to two hours to do if done slowly and precisely.

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post #12 of 21 Old 06-07-2004, 07:25 AM
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Took me 5 days, and cost $60. Nothing went right as usual. The hose clamps were horribly positioned, I had to cut one off and the other I was able to access with one of the vent tubes out of the way. I couldn't get the two hoses off the tank, the tubes had solidified for some reason and it was impossible. I cut them both and they came right off, hence the $60 price tag. It took 4 days to get the new hoses in at the stealer's, hence the 5 days. The vent tube itself broke off in my pliers 5 times, finally I reeled back and gave it all I had, gashed my hand open when the pliers slipped off. Then I could pull the #$&% thing out. I left it out and no problems yet, $40 at the pump

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post #13 of 21 Old 06-07-2004, 07:44 AM Thread Starter
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I reeled back and gave it all I had, gashed my hand open when the pliers slipped off..

Yeah, I got a few nick and cuts but my Jeep is Red so it's all good
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post #14 of 21 Old 06-07-2004, 12:14 PM
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Just so you guys can get a good laugh, I did the whole procedure, which kind of went alright, until I grab the insert hose with needle-nose pliers, pull, pull, pull, millimeters at a time, until it pops right out - all 2" of it!

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post #15 of 21 Old 09-26-2004, 06:18 AM
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I am half way through this mod--I'm doing it a little differently since I had to drop the tank for another reason. I have to say, the most valuable piece of advice in this writeup is the use of the small wrench on that vent hose clamp. I had sunk about an hour into trying to get it off before I re-read the writeup. 10 minutes with a small wrench and it was off.

Thanks for the write up--they need to put a link to this thread in the Y J FAQ.


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